Skin is composed of two layers: the epidermis (or cuticle) and the dermis. The epidermis is a thin outer layer composed of stratified epithelium. The outermost layer of the epidermis is the stratum corneum which is composed of keratin protein-filled, flattened cells surrounded by thin lipid layers. The cells are believed to be attached to one another by protein connections (desmosomes) between cells. The cells in the deepest portion of the epidermis, the basal layer, multiply and grow, pushing the older cells of the epidermis upward and toward the surface. As these cells move upward they become flattened. The epidermis is generally devoid of blood vessels and depends on blood vessels found in the dermis for nutrition. The more superficial cells of the epidermis, being far removed from the nutrient supply, gradually differentiate, transforming their proteins into keratin. This process of keratinization results in the death of the cells. Keratin is an insoluble proteinaceous material and gives the stratum corneum a horn-like consistency. The outermost dead stratum corneum cells are gradually shed and replaced by more recently keratinized cells.
In normal skin, the stratum corneum is shed as individual cells or as small clusters of cells. Skin problems such as dry skin, psoriasis, ichthyosis, dandruff, acne, callus, photodamaged skin, aged skin, and sunburn can be described as disorders of keratinization in which the shedding of stratum corneum cells at the skin surface is altered relative to normal, young, healthy skin. Such alteration results in large clusters of cells leading to visible scaling of the skin, a build-up of keratinaceous material on the surface or in follicles or ducts and/or a rough texture to the skin surface. These conditions may be improved by removal of the outermost keratinaceous material.
For the foregoing reasons, there is a need for an efficacious agent for removing surface scales from the stratum corneum of mammalian skin.
It is an object of the subject invention to provide topical compositions for desquamation (scale removal) from the stratum corneum of mammalian skin.
It is a further object of the subject invention to provide such compositions which are gentler and less irritating to the skin than existing compositions.
It is also an object of the subject invention to provide methods for removal of scales in mammalian skin.